Running Tempo (RT) workouts – rFTP?

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    I see in the RT workouts it says “Use these tempo sets to confirm or reestablish your Zones.” Other than RT6, RT7, RT15 which have 30-32 mins of Zone 3 (but then have Zone 2 immediately following, which will diminish my ability to hammer 30 mins at threshold power, I’ll have nothing left above Z1 after 30 mins at rFTP), or making a custom RT workout with 30 minutes of Zone 3/Zone Y running after a warmup (which is what I did today) how can I use the other RT workouts as is to confirm or reestablish my Zones? I’m wondering how I can monitor and modify my Zones while doing RT workouts that don’t precisely conform to the rFTP test protocol. (To be honest, the rFTP protocol is just brutal, I reached my highest 5 second HR and 5 min HR of 2020 today, and so rFTP tests are clearly super taxing, and so the idea that I could instead gather the necessary data on my Zones by doing less taxing workouts that are just a standard part of my weekly schedule sounds dreamy!)

    David Warden

    Ted, this is also covered in the same document, Intensity Guidelines for Running:


    If you already know your lactate threshold heart rate (LTHR), you can use it to find your TP with an even shorter field test. After warming up, play with your pace until your heart rate settles in at your previously established LTHR for 10 minutes. Your pace at this heart rate is close to your TP.

    Heart Rate

    The next step is to determine your Lactate Threshold Heart Rate (LTHR) from your TP. To do this, warm up with 10 minutes of easy jogging and then accelerate to your TP on a smooth, flat path or road. Wait for your heart rate to stop increasing and plateau. The number you see after it levels off is your LTHR.

    The Power section also has alternatives, a bit too long to go into here, but much shorter than the full 30-minute test.

    The 30-minute test is still the gold standard, but these other methods will get you to 95% accuracy.



    Thanks, David. Lots to chew on in this area!


    So to confirm, the method recommended above is to take an RT workout, run in Zone 3 at LTHR (the top boundary of Zone 3 by definition based on the last test), and note what the pace and power are at that moment, and then that power is the new rFTP, and that pace is the new TP. Is that right? I guess my question is how if I have 10-20 mins in Zone 3 do I run at a specific heart rate? There is such a lag between pace or power and bpm, right? I’ll speed up and overshoot the bpm, then slow down and bpms will drop below LTHR. I’m imagining this would like like a teenager who is attempting to drive a car for the first time (hard on the gas, hard on the brake, repeat.) Is there a better way that looks at the correlation of pace or power and what HR they bpm they produce? I dunno. I’m just a little skeptical that when told after a warmup to go run 10 mins at my LTHR that I can find the right pace or power in a short run to achieve that bpm. But maybe lots of people are already doing this successfully! If I go run for 10 mins at my rFTP, are there any conclusions I can make based on the HR and pace data I get? I guess there could be a complication because the hilliness of this run could differ from the previous test run and if it’s more hilly, then pace goes down and HR goes up, and vice versa. So, wouldn’t that also be an issue with running at a certain HR – if this were more hilly than previous test, then pace will go down relative to HR? If training with running power, maybe I can semi ignore LTHR and TP if I can training in an area with varying hilliness, and just compare rFTP to RPE? I’m just brainstorming, but circling back to your first idea of running “at LTHR”, is that the best practice for a fitness check? Maybe like my teenage driver analogy, it just takes experience running to zero in on a specific HR (LTHR) during a run? Thanks!

    David Warden


    Yes, you understand the correct method. Maybe this will help clarify the recommendation better. Below are 9 common ways to determine “threshold” ranked in order of accuracy.

    – VT lab test
    – LT lab test
    – 60-min threshold field test (observed)
    – 30-min threshold field test
    – 20-min threshold field test
    – Stryd or Vance power test (power only)
    – Backing in from known pace, power or HR (the topic of this thread)
    – Talk test
    – Estimate from TrainingPeaks, Garmin, Stryd…

    The first 3 are expensive, impractical, or unnecessarily grueling. The 30 and 20-minute tests are cheap, easy, and remarkably accurate and therefore a more practical approach to determining threshold. The Stryd and backing in test are very easy, but accuracy starts to be compromised. Talk test is rising in our estimate as a valid method, and we are considering endorsing it as an option. Estimates from the major platforms are unhelpful.

    The backing in method includes all the disadvantages you outline above (but note we do recommend a “smooth flat path or road”). The document does say that “Repeating your chosen field test in every recovery week (recovery weeks fall ever third or fourth week in our 80/20 Triathlon plans) is the theoretical ideal.” The preferred method is a 20-30 minute TT test every rest week. For many athletes, that’s just too much, so we offer this backing in alternative, which includes some disadvantages you’ve outlined.

    A compromise would be to do the full 30-minute test every other rest week, for example.


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